The present invention relates to a home network system composed of home electric appliances, such as an air conditioner, a refrigerator, and a television set, and a controller controlling those units.
Various methods have been proposed for controlling home electric appliances installed in a house, such as a television set, an air conditioner, and a refrigerator, via the Internet or a cellular phone from outside the home. JP-A-2000-32153 discloses a method for remotely controlling home electric appliances via a cellular phone using a telephone line, and JP-A-2001-331394 discloses a system that allows the user to remotely control home electric appliances by sending an instruction from outside the home to the home network controller via the Internet. The problem with those home networks operable from outside the home is that there is a possibility that a third person maliciously operates home electric appliances. To prevent this possibility, the following technologies are disclosed. JP-A-2001-285962 discloses a technology that prevents an unauthentic unit from setting it up as the authentic controller by analyzing messages transferred over a home network to determine if the controller controlling home electric appliances is authentic. JP-A-2001-258077 discloses a technology that allows the user to use the same remote controller at and away from home and encrypts communication data sent from outside the home for ensuring security.